Stratum corneum intercellular matrix and keratin structures (SC matrix/keratin)

The stratum corneum (SC) is the outermost layer of the epidermis, serving as the body's primary interface with the external environment and its most critical permeability barrier. It is often described using the 'bricks and mortar' model, where the 'bricks' are protein-rich corneocytes filled with keratin filaments and the 'mortar' is an intercellular matrix composed of organized lipid lamellae, including ceramides, cholesterol, and free fatty acids (StatPearls, 'Physiology, Stratum Corneum', 2023). This complex structure is essential for maintaining homeostasis by preventing excessive transepidermal water loss and shielding the body from pathogens, allergens, and mechanical stress (Journal of Clinical and Aesthetic Dermatology, 'The Stratum Corneum: The Bricks and Mortar Model', 2012). In dermatological diseases such as atopic dermatitis and psoriasis, the SC is often structurally compromised, leading to inflammation and impaired barrier function. Therapeutic interventions target the SC to either restore its integrity through emollients and barrier-repair lipids or to modify its structure using keratolytic agents like salicylic acid to treat hyperkeratotic conditions (PubMed, 'The skin barrier', Proksch et al., 2008).

Other names

Skin barrierCornified layerHorny layerEpidermal permeability barrierCorneocyte-lipid complex

Drugs targeting this structure act through keratolysis (dissolving the intercellular cement holding keratinocytes), humectancy (binding water within the matrix), occlusion (forming a physical barrier to prevent water loss), or lipid replenishment (restoring the lamellar bilayer integrity). Penetration enhancers may also transiently fluidize the lipid matrix to facilitate the delivery of other pharmacological agents.